The invention relates to a system for measuring strain on thin flexible specimens and more particular to a system for measuring strain of such specimen without the application of a strain element onto the specimen.
Heretofore strain has been determined on some elements by resistance elements attached to the surface of the element to be tested. Other methods include fatigue machines, as well as optical systems. Such systems have been set forth in an article, "Flexural Fatigue Machine for High Temperature Operation at Resonance in Vacuum" by Achter et al, Review of Scientific Instruments, No. 37, page 311, March 1966; and an article "An Optical Technique for the Measurement of Plastic Bending Strains at Elevated Temperature," by Danek et al; NRL Report 5661, August 1961, published by the Naval Research Laboratory, Washington, D.C. 20375. When some types of strain gages are applied to thin elements, the strain gages strengthen the test sample therefore a true test is not obtained.
In carrying out some research, it is necessary that the test be carried out in a vacuum, at high temperatures, and sometimes require remote operation because of radioactive materials. Prior art strain test devices are not suitable for all of the above; therefore a new system has been developed which is suitable for the above situations.